A novel micro-foam film for photovoltaic modules and its preparation process

Abstract

The present invention relates to the field of photovoltaic film technology, in particular to the field of IPCC09J7, and more specifically to a novel micro-foam film for photovoltaic modules and a preparation process thereof. The micro-foam film includes a three-layer structure: the middle layer is a PVDC or EVOH film, and the upper and lower layers are POE films; the POE film is prepared by raw materials, by weight, including: 50-80 parts of polyolefin elastomer, 5-10 parts of vinyl polymer, 1-5 parts of foaming agent, 5-10 parts of filler, and 0.01-0.3 parts of antioxidant. The foaming agent is azodicarbonamide and 4,4-oxybisbenzenesulfonylhydrazine, and the mass ratio of azodicarbonamide and 4,4-oxybisbenzenesulfonylhydrazine is 1: (4-8), so that the foam film is subjected to temperature and external force changes, and the film as a whole has higher stability, reduces the generation of local damage, and ensures the cushioning performance and temperature resistance of the foam film.

Description

Technical Field

[0001] The present invention relates to the field of photovoltaic film technology, in particular to the field of IPCC09J7, and more specifically to a novel micro-foamed film for photovoltaic modules and a preparation process thereof. Background Art

[0002] Photovoltaic film plays a key role in the encapsulation of photovoltaic modules and is a component of these materials. The film bonds photovoltaic cells, photovoltaic glass, and modules, primarily protecting the cells and encapsulating them into photovoltaic modules capable of outputting direct current (DC). Traditional photovoltaic film is made from EVA (ethylene-vinyl acetate) polymer. However, the polar chemical structure of vinyl acetate results in high water vapor transmission rates and susceptibility to hydrolysis and aging. This makes it ineffective in protecting photovoltaic modules in humid outdoor environments. In recent years, POE (ethylene-octene copolymer) photovoltaic film has emerged. Because POE has an all-carbon-carbon and carbon-hydrogen structure, is non-polar, has a low water vapor transmission rate, and is resistant to hydrolysis and aging, the use of POE photovoltaic film has become a major trend in the photovoltaic industry.

[0003] CN202011015244.9 discloses a photovoltaic film resistant to mechanical shock and its preparation method. The invention involves mixing an elastomeric resin of specific raw materials, a hot-melt thermosetting resin, and glass fiber, and subjecting the mixture to casting, embossing, and shaping to produce the film. However, this invention does not address the problem of photovoltaic films being prone to delamination under temperature fluctuations, which reduces their water vapor barrier properties and cannot meet the requirements for use in harsh outdoor environments. Summary of the Invention

[0004] In order to solve the above problems, the first aspect of the present invention provides a new type of micro-foam film for photovoltaic modules, wherein the micro-foam film comprises a three-layer structure: the middle layer is a PVDC or EVOH film, and the upper and lower layers are POE films; the raw materials for preparing the POE film include, by weight: 50-80 parts of polyolefin elastomer, 5-10 parts of vinyl polymer, 1-5 parts of foaming agent, 5-10 parts of filler, and 0.01-0.3 parts of antioxidant.

[0005] Preferably, the polyolefin elastomer has a melt index (measured according to GB3682-2000) of 1-10 g / 10 min and a density of 0.850-0.885 g / cm 3 .

[0006] More preferably, the polyolefin elastomer has a melt index of 1-5 g / 10 min and a density of 0.860-0.885 g / cm 3 .

[0007] More preferably, the polyolefin elastomer has a melt index of 1.1 g / 10 min and a density of 0.883 g / cm 3 , Brand: Borealis Plastomer, Model: Queo 8201.

[0008] The vinyl polymer is a combination of at least one of polar modified polyethylene, low density polyethylene, high density polyethylene, ultra-high molecular weight polyethylene, and ethylene-vinyl acetate copolymer.

[0009] Based on the system of the present invention, by introducing polar modified polyethylene, especially maleic anhydride grafted polyethylene with a melt index of 1.0-5.0g / 10min, and coordinating with the polyolefin elastomer in the system, good compatibility with the foaming agent, antioxidant and filler in the system is achieved, thereby ensuring the bonding performance, mechanical properties and temperature resistance of the foamed rubber.

[0010] Preferably, the vinyl polymer is polar modified polyethylene with a melt index (determined according to GB3682-2000) of 1-5 g / 10 min.

[0011] More preferably, the vinyl polymer is maleic anhydride grafted polyethylene with a melt index of 1-3 g / 10 min.

[0012] More preferably, the vinyl polymer is maleic anhydride grafted polyethylene with a melt index of 2 g / 10 min, purchased from Nanjing Feiteng New Material Technology Co., Ltd.

[0013] Preferably, the mass ratio of the polyolefin elastomer to the vinyl polymer is (8-10):1.

[0014] Further preferably, the mass ratio of the polyolefin elastomer to the vinyl polymer is 9:1.

[0015] The foaming agent includes at least one of an azo compound, a nitrite compound, a hydrazide foaming agent, an inorganic foaming agent, and a physical foaming agent, or a combination of several of the above.

[0016] Preferably, the foaming agent is at least one of azodicarboxylic acid amide, diisopropyl azodicarboxylate, azobisisobutyronitrile, barium azodicarboxylate, N,N'-dinitrosopentamethylenetetramine, N,N'-dinitrosoterephthalamide, p-toluenesulfonylhydrazide, phenylsulfonylhydrazide, 4,4-oxobisbenzenesulfonylhydrazide, sodium bicarbonate, and n-hexane.

[0017] The applicant has found that the foaming agent is azodicarbonamide and 4,4-oxobisbenzenesulfonylhydrazine, and when the mass ratio of azodicarbonamide and 4,4-oxobisbenzenesulfonylhydrazine is 1:(4-8), the foam film has a higher stability as a whole when subjected to temperature and external force changes, reduces the occurrence of local damage, and ensures the cushioning performance and temperature resistance of the foam film. It is speculated that the pore size and uniformity of the foam film affect the comprehensive performance of the film. Based on the system of the present invention, by using azodicarbonamide with a mass ratio of 1:(4-8) The foaming agent combination of azodicarbonamide and 4,4-oxobisbenzenesulfonylhydrazide, in particular, the combination of azodicarbonamide low-temperature foaming agent with a median particle size (D50) of 7.0-9.0 μm and 4,4-oxobisbenzenesulfonylhydrazide with an average particle size of 12-14 μm, ensures that the pore diameters of the prepared film are uniformly distributed and the average pore diameter is within the range of 0.02-0.03 mm. This ensures that the foamed film has high overall stability when subjected to temperature and external force changes, reduces the occurrence of local damage, and ensures the cushioning and temperature resistance of the foamed film. The inventors analyzed that the reason may be: by controlling the mass ratio of azodicarbonamide and 4,4-oxybisbenzenesulfonylhydrazine to be introduced into the polymer system, the combination has improved foaming ratio and foam structure stability, especially controlling the particle size of azodicarbonamide and 4,4-oxybisbenzenesulfonylhydrazine. Under the joint action of maleic anhydride grafted polyethylene, azodicarbonamide and 4,4-oxybisbenzenesulfonylhydrazine are uniformly dispersed in the polymer system to form a fine, high-quality and uniform pore structure, and the bubbles are evenly distributed in the polymer matrix, effectively reducing the reduction in the bonding strength, mechanical properties and heat resistance of the foamed adhesive caused by bubble merging and enrichment.

[0018] More preferably, the foaming agent is azodicarbonamide and 4,4-oxobisbenzenesulfonylhydrazide, and the mass ratio of azodicarbonamide to 4,4-oxobisbenzenesulfonylhydrazide is 1:(4-8).

[0019] Further preferably, the foaming agent is azodicarbonamide (CAS: 123-77-3) and 4,4-oxobisbenzenesulfonylhydrazide (CAS: 80-51-3), and the mass ratio of the azodicarbonamide to the 4,4-oxobisbenzenesulfonylhydrazide is 1:6.

[0020] The cross-linking agent includes at least one of benzoyl peroxide, dicumyl peroxide, tert-butyl peroxyisononanoate, tert-butyl peroxymaleate, and tert-butyl peroxyisopropyl carbonate.

[0021] Preferably, the cross-linking agent comprises dicumyl peroxide and tert-butyl peroxyisononanoate, and the weight ratio of the dicumyl peroxide to tert-butyl peroxyisononanoate is 1:(1-2.2).

[0022] Further preferably, the cross-linking agent includes dicumyl peroxide and tert-butyl peroxyisononanoate, and the weight ratio of the dicumyl peroxide to tert-butyl peroxyisononanoate is 1:1.5.

[0023] The cross-linking auxiliary agent includes at least one of triallyl cyanurate, triallyl isocyanurate, ethylene glycol diethyl diallyl ether, ethylene glycol dimethacrylate, methylene bisacrylamide, and ethoxylated trimethylolpropane triacrylate.

[0024] Preferably, the cross-linking auxiliary agent includes triallyl cyanurate.

[0025] Preferably, the median particle size (D50) of the azodicarbonamide is 5.0-15.0 μm, and the average particle size of the 4,4-oxobisbenzenesulfonylhydrazide is 10-20 μm.

[0026] Further preferably, the median particle size (D50) of the azodicarbonamide is 8 μm, purchased from Guangdong Duba New Material Technology Co., Ltd.; the average particle size of the 4,4-oxobisbenzenesulfonylhydrazine is 13 μm, purchased from Guangdong Duba New Material Technology Co., Ltd.

[0027] The filler includes at least one of titanium dioxide, glass beads, talc, silicon dioxide, aluminum oxide, molybdenum disulfide, and carbon black.

[0028] The applicant has discovered that a combination of 0.2-40 μm glass microbeads treated with a vinyl silane coupling agent, talc, and aluminum oxide is used to fill and modify polyolefin elastomers and vinyl polymers, thereby reducing the raw material usage cost of the polyolefin elastomer while imparting improved reflective effects, thermal conductivity, and heat resistance to the micro-foam film, effectively dissipating heat from the battery and providing a good buffering effect. In particular, when the mass ratio of the glass microbeads, talc, and aluminum oxide is controlled to be (1-3):(5-10):1, the reflective properties, thermal conductivity, heat resistance, and mechanical properties of the micro-foam film are balanced, avoiding increased film brittleness that reduces the impact resistance of the film, and also improving the water vapor barrier performance of the film. The inventors analyzed the possible reasons for this: 0.2-40μm glass microspheres, talc, and aluminum oxide, surface-treated with a vinyl silane coupling agent, are uniformly dispersed in the polymer system under the combined action of polar-modified polyethylene. According to heterogeneous nucleation theory, cell nuclei preferentially form on the surface of the filler. The closed-cell bubbles formed by the foaming agent, supported by the glass microspheres, talc, and aluminum oxide, effectively improve the film's impact resistance and heat deformation temperature while enabling it to stably and effectively perform its thermal conductivity and light reflection properties, making the resulting film more suitable for use in photovoltaic modules. Further research revealed that a mass ratio of glass microspheres, talc, and aluminum oxide of 2:7:1 further improved the film's water vapor barrier properties, likely due to reduced interlayer defects between the POE film layer and the PVDC or EVOH interlayer.

[0029] Preferably, the particle size of the filler is 0.2-40 μm.

[0030] More preferably, the filler has a particle size of 2-35 μm.

[0031] Preferably, the filler is glass microspheres, talc powder and aluminum oxide, and the mass ratio of the glass microspheres, talc powder and aluminum oxide is (1-3): (5-10):1.

[0032] Further preferably, the fillers are glass microbeads, talcum powder and aluminum oxide, all of which are soaked in a vinyl silane coupling agent for 24 hours, and the mass ratio of the glass microbeads, talcum powder and aluminum oxide is 2:7:1.

[0033] Preferably, the vinyl silane coupling agent is vinyl trimethoxy silane (CAS: 2768-02-7).

[0034] The glass microbeads have a particle size of 33 μm and are purchased from Shijiazhuang Yuanjing Mineral Products Co., Ltd.

[0035] The talc powder has a particle size of 6.5 μm and is purchased from Shijiazhuang Hualang Mineral Products Trading Co., Ltd.

[0036] The aluminum oxide has a particle size of 2.5 μm and is purchased from Guangzhou Changyu Chemical Co., Ltd.

[0037] Preferably, the antioxidant auxiliary agent includes an antioxidant and a light stabilizer, and the weight ratio of the antioxidant to the light stabilizer is 1:(0.5-1.8).

[0038] Further preferably, the antioxidant aid includes an antioxidant and a light stabilizer, and the weight ratio of the antioxidant to the light stabilizer is 1:1.2.

[0039] The antioxidant includes one or more of tetrakis[β-(3.5-di-tert-butyl, 4-hydroxyphenyl) propionate] pentaerythritol; β-(3.5-di-tert-butyl, 4-hydroxyphenyl) propionate; tris(2,4-di-tert-butylphenyl) phosphite; butyl octylated diphenylamine, and N,N-di-sec-butylphenylenediamine.

[0040] Preferably, the antioxidant comprises pentaerythritol tetrakis[β-(3.5-di-tert-butyl, 4-hydroxyphenyl) propionate] and tris(2.4-di-tert-butylphenyl) phosphite, and the weight ratio of the pentaerythritol tetrakis[β-(3.5-di-tert-butyl, 4-hydroxyphenyl) propionate] and tris(2.4-di-tert-butylphenyl) phosphite is 1:(1-3).

[0041] Further preferably, the weight ratio of the tetrakis[β-(3,5-di-tert-butyl, 4-hydroxyphenyl) propionate] pentaerythritol and tris(2,4-di-tert-butylphenyl) phosphite is 1:2, and both are purchased from Jiyi Holding Group.

[0042] The light stabilizer is benzophenone or benzotriazole.

[0043] Preferably, the light stabilizer includes one or more of 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole (CAS: 2896-11-5), 2-(2'-hydroxy-5'-methylphenyl)benzotriazole (CAS: 2440-22-4), and 2,2'-dihydroxy-4,4'-dimethoxybenzophenone (CAS: 131-54-4).

[0044] More preferably, the light stabilizer is 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole (CAS: 2896-11-5).

[0045] A second aspect of the present invention provides a process for preparing a novel micro-foam film for photovoltaic modules, comprising the following steps:

[0046] S1, uniformly mixing a polyolefin elastomer, a vinyl polymer, a foaming agent, a filler, and an antioxidant to obtain a mixture;

[0047] S2, using a three-layer co-extrusion process, the mixed material is used as the upper and lower layers, and PVDC or EVOH is used as the middle layer, and is respectively put into three screw extruders for plasticization and extrusion molding.

[0048] The extrusion temperature is 80-100°C.

[0049] Preferably, the extrusion temperature is 90°C.

[0050] Beneficial effects:

[0051] 1. A combination of 0.2-40μm glass microbeads treated with vinyl silane coupling agent, talc powder and aluminum oxide is used to fill and modify polyolefin elastomers and vinyl polymers, reducing the raw material usage cost of polyolefin elastomers while giving the micro-foam film improved reflective effect, thermal conductivity and heat resistance, effectively dissipating heat from the battery and playing a good buffering role.

[0052] 2. When the foaming agent is azodicarbonamide and 4,4-oxobisbenzenesulfonylhydrazine, and the mass ratio of azodicarbonamide to 4,4-oxobisbenzenesulfonylhydrazine is 1:(4-8), the foam film has a higher overall stability when subjected to changes in temperature and external force, reduces the occurrence of local damage, and ensures the cushioning performance and temperature resistance of the foam film.

[0053] 3. Setting the middle layer to PVDC or EVOH can further reduce the water vapor transmission rate and achieve a high barrier technical effect. DETAILED DESCRIPTION

[0054] Example 1

[0055] A novel micro-foam film for photovoltaic modules comprises a three-layer structure: a middle layer of PVDC film, and upper and lower layers of POE film; the raw materials for preparing the POE film include, by weight, 72 parts of polyolefin elastomer, 8 parts of vinyl polymer, 2 parts of foaming agent, 8 parts of filler, 0.9 part of cross-linking agent, 0.2 part of cross-linking aid, and 0.1 part of antioxidant.

[0056] The polyolefin elastomer has a melt index of 1.1 g / 10 min and a density of 0.883 g / cm 3 , Brand: Borealis Plastomer, Model: Queo 8201.

[0057] The vinyl polymer is maleic anhydride grafted polyethylene with a melt index (190° C.) of 2 g / 10 min, purchased from Nanjing Feiteng New Material Technology Co., Ltd.

[0058] The cross-linking agent includes dicumyl peroxide and tert-butyl peroxyisononanoate, and the weight ratio of the dicumyl peroxide to tert-butyl peroxyisononanoate is 1:1.5.

[0059] The cross-linking auxiliary agent includes triallyl cyanurate.

[0060] The foaming agent is azodicarbonamide (CAS: 123-77-3) and 4,4-oxobisbenzenesulfonylhydrazide (CAS: 80-51-3), and the mass ratio of the azodicarbonamide to the 4,4-oxobisbenzenesulfonylhydrazide is 1:6.

[0061] The median particle size (D50) of the azodicarbonamide is 8 μm, which is purchased from Guangdong Duba New Material Technology Co., Ltd.; the average particle size of the 4,4-oxobisbenzenesulfonylhydrazine is 13 μm, which is purchased from Guangdong Duba New Material Technology Co., Ltd.

[0062] The fillers are glass microbeads, talcum powder and aluminum oxide, all of which are soaked in a vinyl silane coupling agent for 24 hours. The mass ratio of the glass microbeads, talcum powder and aluminum oxide is 2:7:1.

[0063] The vinyl silane coupling agent is vinyl trimethoxy silane (CAS: 2768-02-7).

[0064] The glass microbeads have a particle size of 33 μm and are purchased from Shijiazhuang Yuanjing Mineral Products Co., Ltd.

[0065] The talc powder has a particle size of 6.5 μm and is purchased from Shijiazhuang Hualang Mineral Products Trading Co., Ltd.

[0066] The aluminum oxide has a particle size of 2.5 μm and is purchased from Guangzhou Changyu Chemical Co., Ltd.

[0067] The antioxidant auxiliary agent includes an antioxidant and a light stabilizer, and the weight ratio of the antioxidant to the light stabilizer is 1:1.2.

[0068] The antioxidant includes pentaerythritol tetrakis[β-(3.5-di-tert-butyl, 4-hydroxyphenyl) propionate] and tris(2.4-di-tert-butylphenyl) phosphite, and the weight ratio of the pentaerythritol tetrakis[β-(3.5-di-tert-butyl, 4-hydroxyphenyl) propionate] and tris(2.4-di-tert-butylphenyl) phosphite is 1:2, and both are purchased from Jiyi Holding Group.

[0069] The light stabilizer is 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole (CAS: 2896-11-5).

[0070] A preparation process for a novel micro-foam film for photovoltaic modules comprises the following steps:

[0071] S1, uniformly mixing a polyolefin elastomer, a vinyl polymer, a foaming agent, a filler, a crosslinking agent, a crosslinking aid, and an antioxidant to obtain a mixture;

[0072] S2, using a three-layer co-extrusion process, the mixed material is used as the upper and lower layers, and PVDC is used as the middle layer, and is respectively put into three screw extruders for plasticization and extrusion molding.

[0073] The PVDC extrusion temperature is 190°C; the mixed material extrusion temperature is 90°C.

[0074] Example 2

[0075] A novel micro-foam film for photovoltaic modules comprises a three-layer structure: an EVOH film as the middle layer and POE films as the upper and lower layers; the raw materials for preparing the POE film include, by weight, 72 parts of a polyolefin elastomer, 8 parts of a vinyl polymer, 2 parts of a foaming agent, 8 parts of a filler, 0.9 parts of a cross-linking agent, 0.2 parts of a cross-linking aid, and 0.1 parts of an antioxidant.

[0076] The polyolefin elastomer has a melt index of 1.1 g / 10 min and a density of 0.883 g / cm 3 , Brand: Borealis Plastomer, Model: Queo 8201.

[0077] The vinyl polymer is maleic anhydride grafted polyethylene with a melt index of 2 g / 10 min, purchased from Nanjing Feiteng New Material Technology Co., Ltd.

[0078] The cross-linking agent includes dicumyl peroxide and tert-butyl peroxyisononanoate, and the weight ratio of the dicumyl peroxide to tert-butyl peroxyisononanoate is 1:1.5.

[0079] The cross-linking auxiliary agent includes triallyl cyanurate.

[0080] The foaming agent is azodicarbonamide (CAS: 123-77-3) and 4,4-oxobisbenzenesulfonylhydrazide (CAS: 80-51-3), and the mass ratio of the azodicarbonamide to the 4,4-oxobisbenzenesulfonylhydrazide is 1:6.

[0081] The median particle size (D50) of the azodicarbonamide is 8 μm, which is purchased from Guangdong Duba New Material Technology Co., Ltd.; the average particle size of the 4,4-oxobisbenzenesulfonylhydrazine is 13 μm, which is purchased from Guangdong Duba New Material Technology Co., Ltd.

[0082] The fillers are glass microbeads, talcum powder and aluminum oxide, all of which are soaked in a vinyl silane coupling agent for 24 hours. The mass ratio of the glass microbeads, talcum powder and aluminum oxide is 2:7:1.

[0083] The vinyl silane coupling agent is vinyl trimethoxy silane (CAS: 2768-02-7).

[0084] The glass microbeads have a particle size of 33 μm and are purchased from Shijiazhuang Yuanjing Mineral Products Co., Ltd.

[0085] The talc powder has a particle size of 6.5 μm and is purchased from Shijiazhuang Hualang Mineral Products Trading Co., Ltd.

[0086] The aluminum oxide has a particle size of 2.5 μm and is purchased from Guangzhou Changyu Chemical Co., Ltd.

[0087] The antioxidant auxiliary agent includes an antioxidant and a light stabilizer, and the weight ratio of the antioxidant to the light stabilizer is 1:1.2.

[0088] The antioxidant includes pentaerythritol tetrakis[β-(3.5-di-tert-butyl, 4-hydroxyphenyl) propionate] and tris(2.4-di-tert-butylphenyl) phosphite, and the weight ratio of the pentaerythritol tetrakis[β-(3.5-di-tert-butyl, 4-hydroxyphenyl) propionate] and tris(2.4-di-tert-butylphenyl) phosphite is 1:2, and both are purchased from Jiyi Holding Group.

[0089] The light stabilizer is 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole (CAS: 2896-11-5).

[0090] A preparation process for a novel micro-foam film for photovoltaic modules comprises the following steps:

[0091] S1, uniformly mixing a polyolefin elastomer, a vinyl polymer, a foaming agent, a filler, a crosslinking agent, a crosslinking aid, and an antioxidant to obtain a mixture;

[0092] S2, using a three-layer co-extrusion process, the mixed material is used as the upper and lower layers, and EVOH is used as the middle layer, and is respectively put into three screw extruders for plasticization and extrusion molding.

[0093] The EVOH extrusion temperature is 200°C; the mixed material extrusion temperature is 90°C.

[0094] Example 3

[0095] The specific implementation is the same as that of Example 1; except that the foaming agent in Example 3 is azodicarbonamide (CAS: 123-77-3) and 4,4-oxobisbenzenesulfonylhydrazide (CAS: 80-51-3), and the mass ratio of azodicarbonamide to 4,4-oxobisbenzenesulfonylhydrazide is 1:4.

[0096] Comparative Example 1

[0097] The specific implementation is the same as Example 1; the difference is that the mass ratio of azodicarbonamide and 4,4-oxobisbenzenesulfonylhydrazide in Comparative Example 1 is 1:10.

[0098] Comparative Example 2

[0099] The specific implementation is the same as Example 1; the difference is that the mass ratio of the glass microbeads, talc powder and aluminum oxide in Comparative Example 2 is 1:7:3.

[0100] Comparative Example 3

[0101] The specific implementation is the same as Example 1; the difference is that the mass ratio of the glass microbeads, talc powder and aluminum oxide in Comparative Example 3 is 7:2:1.

[0102] Performance testing methods

[0103] Sample preparation process: The films prepared in Examples 1-3 and Comparative Examples 1-3 were subjected to high-temperature foaming and cross-linking. The temperature for high-temperature foaming and cross-linking was 160°C, and the time for high-temperature foaming and cross-linking was 5 minutes. The following tests were performed, wherein the sample specifications were in the shape of 15mm×200mm strips.

[0104] 1. Adhesion: The adhesion between the component (BBF type component produced by 3M) and the sample was tested in accordance with GB / T2790-1995 using a universal tensile testing machine (WY-2000A) at a tensile rate of 100 mm / min. The test results are recorded in Table 1.

[0105] 2. Interlayer Peel Strength: Tested according to GB-T 2790-1995, Adhesives, 180° Peel Strength Test Method - Flexible Material Against Rigid Material. Clamp the unbonded ends of the sample symmetrically between the upper and lower clamps of a universal testing machine, ensuring no slippage. Operate the machine, separating the upper and lower clamps at a rate of 100 mm / min. The machine reports the interlayer peel strength of the material. The test results are recorded in Table 1.

[0106] 3. Density test: Test in accordance with GB-T 533-1991. The test results are recorded in Table 1.

[0107] 4. Average Cell Diameter: The specimens were fully cooled in liquid nitrogen and then fractured. The cross-sections were then sputtered with gold and observed using a scanning electron microscope (SEM) to obtain images. The number and diameter of cells in the SEM images were counted using Image J software, and the average values were calculated. The percentage of cells with diameters between 0.01 and 0.04 mm was also calculated. The test results are reported in Table 1.

[0108] 5. Water vapor transmission rate: Measured using a water vapor transmission rate meter (SYSTESTER, WVTR).

[0109] Performance test data

[0110] Table 1

[0111]

Claims

1. A micro-foam film for photovoltaic modules, characterized in that: The micro-foam film comprises a three-layer structure: a middle layer of PVDC or EVOH film, and upper and lower layers of POE film; the raw materials for preparing the POE film, in parts by weight, include: 50-80 parts of polyolefin elastomer, 5-10 parts of vinyl polymer, 1-5 parts of foaming agent, 5-10 parts of filler, 0.5-1.5 parts of cross-linking agent, 0.1-0.6 parts of cross-linking auxiliary agent, and 0.01-0.3 parts of antioxidant auxiliary agent; The foaming agent is azodicarbonamide and 4,4-oxobisbenzenesulfonylhydrazide, and the mass ratio of azodicarbonamide to 4,4-oxobisbenzenesulfonylhydrazide is 1:(4-8); The median particle size of the azodicarbonamide is 7.0-9.0 μm; the average particle size of the 4,4-oxobisbenzenesulfonylhydrazine is 12-14 μm; The filler comprises glass microspheres, talc powder and aluminum oxide, and the mass ratio of the glass microspheres, talc powder and aluminum oxide is (1-3): (5-10):

1.

2. The micro-foam film for photovoltaic modules according to claim 1, characterized in that: The polyolefin elastomer has a melt index of 1-10 g / 10 min and a density of 0.850-0.885 g / cm 3 .

3. The micro-foam film for photovoltaic modules according to claim 1, characterized in that: The mass ratio of the polyolefin elastomer to the vinyl polymer is (8-10):

1.

4. The micro-foam film for photovoltaic modules according to claim 1, characterized in that: The particle size of the filler is 0.2-40 μm.

5. The micro-foam film for photovoltaic modules according to claim 1, characterized in that: The particle size of the filler is 2-35 μm.

6. The micro-foam film for photovoltaic modules according to claim 1, characterized in that: The antioxidant auxiliary agent includes an antioxidant and a light stabilizer, and the weight ratio of the antioxidant to the light stabilizer is 1:(0.5-1.8).

7. A process for preparing the micro-foam film for photovoltaic modules according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1, uniformly mixing a polyolefin elastomer, a vinyl polymer, a foaming agent, a filler, a crosslinking agent, a crosslinking aid, and an antioxidant to obtain a mixture; S2, using a three-layer co-extrusion process, the mixed material is used as the upper and lower layers, and PVDC or EVOH is used as the middle layer, and is respectively put into three screw extruders for plasticization and extrusion molding.

8. The process for preparing a micro-foam film for photovoltaic modules according to claim 7, characterized in that: The extrusion temperature is 80-100°C.

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